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-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
-NNAAMMEE
- dhcpd.conf - dhcpd configuration file
-
-DDEESSCCRRIIPPTTIIOONN
- The dhcpd.conf file contains configuration information for
- _d_h_c_p_d_, the Internet Software Consortium DHCP Server.
-
- The dhcpd.conf file is a free-form ASCII text file. It
- is parsed by the recursive-descent parser built into
- dhcpd. The file may contain extra tabs and newlines for
- formatting purposes. Keywords in the file are case-
- insensitive. Comments may be placed anywhere within the
- file (except within quotes). Comments begin with the #
- character and end at the end of the line.
-
- The file essentially consists of a list of statements.
- Statements fall into two broad categories - parameters and
- declarations.
-
- Parameter statements either say how to do something (e.g.,
- how long a lease to offer), whether to do something (e.g.,
- should dhcpd provide addresses to unknown clients), or
- what parameters to provide to the client (e.g., use gate-
- way 220.177.244.7).
-
- Declarations are used to describe the topology of the net-
- work, to describe clients on the network, to provide
- addresses that can be assigned to clients, or to apply a
- group of parameters to a group of declarations. In any
- group of parameters and declarations, all parameters must
- be specified before any declarations which depend on those
- parameters may be specified.
-
- Declarations about network topology include the _s_e_r_v_e_r_-
- _i_d_e_n_t_i_f_i_e_r, the _s_h_a_r_e_d_-_n_e_t_w_o_r_k and the _s_u_b_n_e_t declara-
- tions. If clients on a subnet are to be assigned
- addresses dynamically, a _r_a_n_g_e declaration must appear
- within the _s_u_b_n_e_t declaration. For clients with stati-
- cally assigned addresses, or for installations where only
- known clients will be served, each such client must have a
- _h_o_s_t declaration. If parameters are to be applied to a
- group of declarations which are not related strictly on a
- per-subnet basis, the _g_r_o_u_p declaration can be used.
-
- Each dhcpd.conf file must have one (and only one) _s_e_r_v_e_r_-
- _i_d_e_n_t_i_f_i_e_r declaration, which tells dhcpd the identifier
- to use when issuing leases. For every subnet which will
- be served, and for every subnet to which the dhcp server
- is connected, there must be one _s_u_b_n_e_t declaration, which
- tells dhcpd how to recognize that an address is on that
- subnet. A _s_u_b_n_e_t declaration is required for each subnet
- even if no addresses will be dynamically allocated on that
- subnet.
-
-
-
-
- 1
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- Some installations have physical networks on which more
- than one IP subnet operates. For example, if there is a
- site-wide requirement that 8-bit subnet masks be used, but
- a department with a single physical ethernet network
- expands to the point where it has more than 254 nodes, it
- may be necessary to run two 8-bit subnets on the same eth-
- ernet until such time as a new physical network can be
- added. In this case, the _s_u_b_n_e_t declarations for these
- two networks may be enclosed in a _s_h_a_r_e_d_-_n_e_t_w_o_r_k declara-
- tion.
-
- Some sites may have departments which have clients on more
- than one subnet, but it may be desirable to offer those
- clients a uniform set of parameters which are different
- than what would be offered to clients from other depart-
- ments on the same subnet. For clients which will be
- declared explicitly with _h_o_s_t declarations, these declara-
- tions can be enclosed in a _g_r_o_u_p declaration along with
- the parameters which are common to that department. For
- clients whose addresses will be dynamically assigned,
- there is currently no way to group parameter assignments
- other than by network topology.
-
- When a client is to be booted, its boot parameters are
- determined by first consulting that client's _h_o_s_t declara-
- tion (if any), then consulting the _g_r_o_u_p declaration (if
- any) which enclosed that _h_o_s_t declaration, then consulting
- the _s_u_b_n_e_t declaration for the subnet on which the client
- is booting, then consulting the _s_h_a_r_e_d_-_n_e_t_w_o_r_k declaration
- (if any) containing that subnet, and finally consulting
- the top-level parameters which may be specified outside of
- any declaration.
-
- When dhcpd tries to find a _h_o_s_t declaration for a client,
- it first looks for a _h_o_s_t declaration which has a _f_i_x_e_d_-
- _a_d_d_r_e_s_s parameter which matches the subnet or shared net-
- work on which the client is booting. If it doesn't find
- any such entry, it then tries to find an entry which has
- no _f_i_x_e_d_-_a_d_d_r_e_s_s parameter. If no such entry is found,
- then dhcpd acts as if there is no entry in the dhcpd.conf
- file for that client, even if there is an entry for that
- client on a different subnet or shared network.
-
-EEXXAAMMPPLLEESS
- A typical dhcpd.conf file will look something like this:
-
- server-identifier dhcps.isc.org;
- _g_l_o_b_a_l _p_a_r_a_m_e_t_e_r_s_._._.
-
- shared-network ISC-BIGGIE {
- _s_h_a_r_e_d_-_n_e_t_w_o_r_k_-_s_p_e_c_i_f_i_c _p_a_r_a_m_e_t_e_r_s_._._.
- subnet 204.254.239.0 netmask 255.255.255.224 {
- _s_u_b_n_e_t_-_s_p_e_c_i_f_i_c _p_a_r_a_m_e_t_e_r_s_._._.
- range 204.254.239.10 204.254.239.30;
-
-
-
- 2
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- }
- subnet 204.254.239.32 netmask 255.255.255.224 {
- _s_u_b_n_e_t_-_s_p_e_c_i_f_i_c _p_a_r_a_m_e_t_e_r_s_._._.
- range 204.254.239.42 204.254.239.62;
- }
- }
-
- subnet 204.254.239.64 netmask 255.255.255.224 {
- _s_u_b_n_e_t_-_s_p_e_c_i_f_i_c _p_a_r_a_m_e_t_e_r_s_._._.
- range 204.254.239.74 204.254.239.94;
- }
-
- group {
- _g_r_o_u_p_-_s_p_e_c_i_f_i_c _p_a_r_a_m_e_t_e_r_s_._._.
- host zappo.test.isc.org {
- _h_o_s_t_-_s_p_e_c_i_f_i_c _p_a_r_a_m_e_t_e_r_s_._._.
- }
- host beppo.test.isc.org {
- _h_o_s_t_-_s_p_e_c_i_f_i_c _p_a_r_a_m_e_t_e_r_s_._._.
- }
- host harpo.test.isc.org {
- _h_o_s_t_-_s_p_e_c_i_f_i_c _p_a_r_a_m_e_t_e_r_s_._._.
- }
- }
-
- Figure 1
-
-
- Notice that after the server-identifier declaration,
- there's a place for global parameters. These might be
- things like the organization's domain name, the addresses
- of the name servers (if they are common to the entire
- organization), and so on. So, for example:
-
- option domain-name "isc.org";
- option name-servers ns1.isc.org, ns2.isc.org;
-
- Figure 2
-
- As you can see in Figure 2, it's legal to specify host
- addresses in parameters as domain names rather than as
- numeric IP addresses. If a given hostname resolves to
- more than one IP address (for example, if that host has
- two ethernet interfaces), both addresses are supplied to
- the client.
-
- In Figure 1, you can see that both the shared-network
- statement and the subnet statements can have parameters.
- Let us say that the shared network _I_S_C_-_B_I_G_G_I_E supports an
- entire department - perhaps the accounting department.
- If accounting has its own domain, then a shared-network-
- specific parameter might be:
-
- option domain-name "accounting.isc.org";
-
-
-
- 3
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- All subnet declarations appearing in the shared-network
- declaration would then have the domain-name option set to
- "accounting.isc.org" instead of just "isc.org".
-
- The most obvious reason for having subnet-specific parame-
- ters as shown in Figure 1 is that each subnet, of neces-
- sity, has its own router. So for the first subnet, for
- example, there should be something like:
-
- option routers 204.254.239.1;
-
- Note that the address here is specified numerically.
- This is not required - if you have a different domain name
- for each interface on your router, it's perfectly legiti-
- mate to use the domain name for that interface instead of
- the numeric address. However, in many cases there may be
- only one domain name for all of a router's IP addresses,
- and it would not be appropriate to use that name here.
-
- In Figure 1 there is also a _g_r_o_u_p statement, which pro-
- vides common parameters for a set of three hosts - zappo,
- beppo and harpo. As you can see, these hosts are all in
- the test.isc.org domain, so it might make sense for a
- group-specific parameter to override the domain name sup-
- plied to these hosts:
-
- option domain-name "test.isc.org";
-
- Also, given the domain they're in, these are probably test
- machines. If we wanted to test the DHCP leasing mecha-
- nism, we might set the lease timeout somewhat shorter than
- the default:
-
- max-lease-time 120;
- default-lease-time 120;
-
- You may have noticed that while some parameters start with
- the _o_p_t_i_o_n keyword, some do not. Parameters starting
- with the _o_p_t_i_o_n keyword correspond to actual DHCP options,
- while parameters that do not start with the option keyword
- either control the behaviour of the DHCP server (e.g., how
- long a lease dhcpd will give out), or specify client
- parameters that are not optional in the DHCP protocol (for
- example, server-name and filename).
-
- In Figure 1, each host had _h_o_s_t_-_s_p_e_c_i_f_i_c _p_a_r_a_m_e_t_e_r_s.
- These could include such things as the _h_o_s_t_n_a_m_e option,
- the name of a file to upload (the _f_i_l_e_n_a_m_e _p_a_r_a_m_e_t_e_r_) _a_n_d
- _t_h_e _a_d_d_r_e_s_s _o_f _t_h_e _s_e_r_v_e_r _f_r_o_m _w_h_i_c_h _t_o _u_p_l_o_a_d _t_h_e _f_i_l_e
- _(_t_h_e _n_e_x_t_-_s_e_r_v_e_r parameter). In general, any parameter
- can appear anywhere that parameters are allowed, and will
- be applied according to the scope in which the parameter
- appears.
-
-
-
-
- 4
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- Imagine that you have a site with a lot of NCD X-
- Terminals. These terminals come in a variety of models,
- and you want to specify the boot files for each models.
- One way to do this would be to have host declarations for
- each server and group them by model:
-
- group {
- filename "Xncd19r";
- next-server ncd-booter;
-
- host ncd1 { hardware ethernet 0:c0:c3:49:2b:57; }
- host ncd4 { hardware ethernet 0:c0:c3:80:fc:32; }
- host ncd8 { hardware ethernet 0:c0:c3:22:46:81; }
- }
-
- group {
- filename "Xncd19c";
- next-server ncd-booter;
-
- host ncd2 { hardware ethernet 0:c0:c3:88:2d:81; }
- host ncd3 { hardware ethernet 0:c0:c3:00:14:11; }
- }
-
- group {
- filename "XncdHMX";
- next-server ncd-booter;
-
- host ncd1 { hardware ethernet 0:c0:c3:11:90:23; }
- host ncd4 { hardware ethernet 0:c0:c3:91:a7:8; }
- host ncd8 { hardware ethernet 0:c0:c3:cc:a:8f; }
- }
-
-RREEFFEERREENNCCEE:: DDEECCLLAARRAATTIIOONNSS
- TThhee _s_e_r_v_e_r_-_i_d_e_n_t_i_f_i_e_r ssttaatteemmeenntt
-
- sseerrvveerr--iiddeennttiiffiieerr _h_o_s_t_n_a_m_e;;
-
- The server-identifier declaration must be used exactly
- once in each dhcpd.conf file to tell dhcpd what IP address
- to use as its server identifier, as required by the DHCP
- protocol. On a machine with a single interface, the
- server identifier should be the primary address of that
- interface. On machines with multiple interfaces, the
- address of one such interface must be chosen. Any
- address may be chosen, as long as it is the address of one
- of the interfaces of that machine.
-
- TThhee _s_h_a_r_e_d_-_n_e_t_w_o_r_k ssttaatteemmeenntt
-
- sshhaarreedd--nneettwwoorrkk _n_a_m_e {{
- [ _p_a_r_a_m_e_t_e_r_s ]
- [ _d_e_c_l_a_r_a_t_i_o_n_s ]
- }}
-
-
-
-
- 5
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- The _s_h_a_r_e_d_-_n_e_t_w_o_r_k statement is used to inform the DHCP
- server that some IP subnets actually share the same physi-
- cal network. Any subnets in a shared network should be
- declared within a _s_h_a_r_e_d_-_n_e_t_w_o_r_k statement. Parameters
- specified in the _s_h_a_r_e_d_-_n_e_t_w_o_r_k statement will be used
- when booting clients on those subnets unless parameters
- provided at the subnet or host level override them. If
- any subnet in a shared network has addresses available for
- dynamic allocation, those addresses are collected into a
- common pool for that shared network and assigned to
- clients as needed. There is no way to distinguish on
- which subnet of a shared network a client should boot.
-
- _N_a_m_e should be the name of the shared network. This name
- is used when printing debugging messages, so it should be
- descriptive for the shared network. The name may have
- the syntax of a valid domain name (although it will never
- be used as such), or it may be any arbitrary name,
- enclosed in quotes.
-
- TThhee _s_u_b_n_e_t ssttaatteemmeenntt
-
- ssuubbnneett _s_u_b_n_e_t_-_n_u_m_b_e_r nneettmmaasskk _n_e_t_m_a_s_k {{
- [ _p_a_r_a_m_e_t_e_r_s ]
- [ _d_e_c_l_a_r_a_t_i_o_n_s ]
- }}
-
- The _s_u_b_n_e_t statement is used to provide dhcpd with enough
- information to tell whether or not an IP address is on
- that subnet. It may also be used to provide subnet-
- specific parameters and to specify what addresses may be
- dynamically allocated to clients booting on that subnet.
- Such addresses are specified using the _r_a_n_g_e declaration.
-
- The _s_u_b_n_e_t_-_n_u_m_b_e_r should be an IP address or domain name
- which resolves to the subnet number of the subnet being
- described. The _n_e_t_m_a_s_k should be an IP address or domain
- name which resolves to the subnet mask of the subnet being
- described. The subnet number, together with the netmask,
- are sufficient to determine whether any given IP address
- is on the specified subnet.
-
- Although a netmask must be given with every subnet decla-
- ration, it is recommended that if there is any variance in
- subnet masks at a site, a subnet-mask option statement be
- used in each subnet declaration to set the desired subnet
- mask, since any subnet-mask option statement will override
- the subnet mask declared in the subnet statement.
-
- TThhee _r_a_n_g_e ssttaatteemmeenntt
-
- rraannggee [ ddyynnaammiicc--bboooottpp ] _l_o_w_-_a_d_d_r_e_s_s [ _h_i_g_h_-_a_d_d_r_e_s_s];;
-
- For any subnet on which addresses will be assigned
-
-
-
- 6
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- dynamically, there must be at least one _r_a_n_g_e statement.
- The range statement gives the lowest and highest IP
- addresses in a range. All IP addresses in the range
- should be in the subnet in which the _r_a_n_g_e statement is
- declared. The _d_y_n_a_m_i_c_-_b_o_o_t_p flag may be specified if
- addresses in the specified range may be dynamically
- assigned to BOOTP clients as well as DHCP clients. When
- specifying a single address, _h_i_g_h_-_a_d_d_r_e_s_s can be omitted.
-
- TThhee _h_o_s_t ssttaatteemmeenntt
-
- hhoosstt _h_o_s_t_n_a_m_e {
- [ _p_a_r_a_m_e_t_e_r_s ]
- [ _d_e_c_l_a_r_a_t_i_o_n_s ]
- }}
-
- There must be at least one hhoosstt statement for every BOOTP
- client that is to be served. hhoosstt statements may also be
- specified for DHCP clients, although this is not required
- unless booting is only enabled for known hosts.
-
- If it is desirable to be able to boot a DHCP or BOOTP
- client on more than one subnet with fixed addresses, more
- than one address may be specified in the _f_i_x_e_d_-_a_d_d_r_e_s_s
- parameter, or more than one hhoosstt statement may be speci-
- fied.
-
- If client-specific boot parameters must change based on
- the network to which the client is attached, then multiple
- hhoosstt statements should be used.
-
- If a client is to be booted using a fixed address if it's
- possible, but should be allocated a dynamic address other-
- wise, then a hhoosstt statement must be specified without a
- ffiixxeedd--aaddddrreessss clause. _h_o_s_t_n_a_m_e should be a name identify-
- ing the host. If a _h_o_s_t_n_a_m_e option is not specified for
- the host, _h_o_s_t_n_a_m_e is used.
-
- _H_o_s_t declarations are matched to actual DHCP or BOOTP
- clients by matching the dhcp-client-identifier option
- specified in the _h_o_s_t declaration to the one supplied by
- the client, or, if the _h_o_s_t declaration or the client does
- not provide a dhcp-client-identifier option, by matching
- the _h_a_r_d_w_a_r_e parameter in the _h_o_s_t declaration to the net-
- work hardware address supplied by the client. BOOTP
- clients do not normally provide a _d_h_c_p_-_c_l_i_e_n_t_-_i_d_e_n_t_i_f_i_e_r,
- so the hardware address must be used for all clients that
- may boot using the BOOTP protocol.
-
- TThhee _g_r_o_u_p ssttaatteemmeenntt
-
- ggrroouupp {
- [ _p_a_r_a_m_e_t_e_r_s ]
- [ _d_e_c_l_a_r_a_t_i_o_n_s ]
-
-
-
- 7
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- }}
-
- The group statement is used simply to apply one or more
- parameters to a group of declarations. It can be used to
- group hosts, shared networks, subnets, or even other
- groups.
-
-RREEFFEERREENNCCEE:: PPAARRAAMMEETTEERRSS
- TThhee _d_e_f_a_u_l_t_-_l_e_a_s_e_-_t_i_m_e ssttaatteemmeenntt
-
- ddeeffaauulltt--lleeaassee--ttiimmee _t_i_m_e;;
-
- _T_i_m_e should be the length in seconds that will be assigned
- to a lease if the client requesting the lease does not ask
- for a specific expiration time.
-
- TThhee _m_a_x_-_l_e_a_s_e_-_t_i_m_e ssttaatteemmeenntt
-
- mmaaxx--lleeaassee--ttiimmee _t_i_m_e;;
-
- _T_i_m_e should be the maximum length in seconds that will be
- assigned to a lease if the client requesting the lease
- asks for a specific expiration time.
-
- TThhee _h_a_r_d_w_a_r_e ssttaatteemmeenntt
-
- hhaarrddwwaarree _h_a_r_d_w_a_r_e_-_t_y_p_e _h_a_r_d_w_a_r_e_-_a_d_d_r_e_s_s;;
-
- In order for a BOOTP client to be recognized, its network
- hardware address must be declared using a _h_a_r_d_w_a_r_e clause
- in the _h_o_s_t statement. _h_a_r_d_w_a_r_e_-_t_y_p_e must be the name of
- a physical hardware interface type. Currently, only the
- eetthheerrnneett type is recognized, although support for ttookkeenn--
- rriinngg and ffddddii hardware types would also be desirable. The
- _h_a_r_d_w_a_r_e_-_a_d_d_r_e_s_s should be a set of hexadecimal octets
- (numbers from 0 through ff) seperated by colons. The
- _h_a_r_d_w_a_r_e_f_R _s_t_a_t_e_m_e_n_t _m_a_y _a_l_s_o _b_e _u_s_e_d _f_o_r _D_H_C_P _c_l_i_e_n_t_s_.
-
- TThhee _f_i_l_e_n_a_m_e ssttaatteemmeenntt
-
- ffiilleennaammee ""_f_i_l_e_n_a_m_e"";;
-
- The _f_i_l_e_n_a_m_e statement can be used to specify the name of
- the initial boot file which is to be loaded by a client.
- The _f_i_l_e_n_a_m_e should be a filename recognizable to whatever
- file transfer protocol the client can be expected to use
- to load the file.
-
- TThhee _s_e_r_v_e_r_-_n_a_m_e ssttaatteemmeenntt
-
- sseerrvveerr--nnaammee ""_n_a_m_e"";;
-
- The _s_e_r_v_e_r_-_n_a_m_e statement can be used to inform the client
- of the name of the server from which it is booting. _N_a_m_e
-
-
-
- 8
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- should be the name that will be provided to the client.
-
- TThhee _n_e_x_t_-_s_e_r_v_e_r ssttaatteemmeenntt
-
- nneexxtt--sseerrvveerr _s_e_r_v_e_r_-_n_a_m_e;;
-
- The _n_e_x_t_-_s_e_r_v_e_r statement is used to specify the host
- address of the server from which the initial boot file
- (specified in the _f_i_l_e_n_a_m_e statement) is to be loaded.
- _S_e_r_v_e_r_-_n_a_m_e should be a numeric IP address or a domain
- name. If no _n_e_x_t_-_s_e_r_v_e_r parameter applies to a given
- client, the address specified in the _s_e_r_v_e_r_-_i_d_e_n_t_i_f_i_e_r
- statement is used.
-
- TThhee _f_i_x_e_d_-_a_d_d_r_e_s_s ssttaatteemmeenntt
-
- ffiixxeedd--aaddddrreessss _a_d_d_r_e_s_s [,, _a_d_d_r_e_s_s ... ];;
-
- The _f_i_x_e_d_-_a_d_d_r_e_s_s statement is used to assign one or more
- fixed IP addresses to a client. It should only appear in
- a _h_o_s_t declaration. If more than one address is supplied,
- then when the client boots, it will be assigned the
- address which corresponds to the network on which it is
- booting. If none of the addresses in the _f_i_x_e_d_-_a_d_d_r_e_s_s
- statement are on the network on which the client is boot-
- ing, that client will not match the _h_o_s_t declaration con-
- taining that _f_i_x_e_d_-_a_d_d_r_e_s_s statement. Each _a_d_d_r_e_s_s should
- be either an IP address or a domain name which resolves to
- one or more IP addresses.
-
- TThhee _d_y_n_a_m_i_c_-_b_o_o_t_p_-_l_e_a_s_e_-_c_u_t_o_f_f ssttaatteemmeenntt
-
- ddyynnaammiicc--bboooottpp--lleeaassee--ccuuttooffff _d_a_t_e;;
-
- The _d_y_n_a_m_i_c_-_b_o_o_t_p_-_l_e_a_s_e_-_c_u_t_o_f_f statement sets the ending
- time for all leases assigned dynamically to BOOTP clients.
- Because BOOTP clients do not have any way of renewing
- leases, and don't know that their leases could expire, by
- default dhcpd assignes infinite leases to all BOOTP
- clients. However, it may make sense in some situations to
- set a cutoff date for all BOOTP leases - for example, the
- end of a school term, or the time at night when a facility
- is closed and all machines are required to be powered off.
-
- _D_a_t_e should be the date on which all assigned BOOTP leases
- will end. The date is specified in the form:
-
- W YYYY/MM/DD HH:MM:SS
-
- W is the day of the week expressed as a number from zero
- (Sunday) to six (Saturday). YYYY is the year, including
- the century. MM is the month expressed as a number from 1
- to 12. DD is the day of the month, counting from 1. HH
- is the hour, from zero to 23. MM is the minute and SS is
-
-
-
- 9
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- the second. The time is always in Greenwich Mean Time
- (GMT), not local time.
-
- TThhee _d_y_n_a_m_i_c_-_b_o_o_t_p_-_l_e_a_s_e_-_l_e_n_g_t_h ssttaatteemmeenntt
-
- ddyynnaammiicc--bboooottpp--lleeaassee--lleennggtthh _l_e_n_g_t_h;;
-
- The _d_y_n_a_m_i_c_-_b_o_o_t_p_-_l_e_a_s_e_-_l_e_n_g_t_h statement is used to set
- the length of leases dynamically assigned to BOOTP
- clients. At some sites, it may be possible to assume
- that a lease is no longer in use if its holder has not
- used BOOTP or DHCP to get its address within a certain
- time period. The period is specified in _l_e_n_g_t_h as a num-
- ber of seconds. If a client reboots using BOOTP during
- the timeout period, the lease duration is reset to _l_e_n_g_t_h,
- so a BOOTP client that boots frequently enough will never
- lose its lease. Needless to say, this parameter should be
- adjusted with extreme caution.
-
- TThhee _b_o_o_t_-_u_n_k_n_o_w_n_-_c_l_i_e_n_t_s ssttaatteemmeenntt
-
- bboooott--uunnkknnoowwnn--cclliieennttss _f_l_a_g;;
-
- The _b_o_o_t_-_u_n_k_n_o_w_n_-_c_l_i_e_n_t_s statement is used to tell dhcpd
- whether or not to dynamically assign addresses to unknown
- clients. If _f_l_a_g is true (the default), then addresses
- are dynamically assigned to unknown clients when avail-
- able. If _f_l_a_g is false, then addresses are provided only
- to clients which match at least one host declaration.
-
- TThhee _g_e_t_-_l_e_a_s_e_-_h_o_s_t_n_a_m_e_s ssttaatteemmeenntt
-
- ggeett--lleeaassee--hhoossttnnaammeess _f_l_a_g;;
-
- The _g_e_t_-_l_e_a_s_e_-_h_o_s_t_n_a_m_e_s statement is used to tell dhcpd
- whether or not to look up the domain name corresponding to
- the IP address of each address in the lease pool and use
- that address for the DHCP _h_o_s_t_n_a_m_e option. If _f_l_a_g is
- true, then this lookup is done for all addresses in the
- current scope. By default, or if _f_l_a_g is false, no
- lookups are done.
-
- TThhee _u_s_e_-_h_o_s_t_-_d_e_c_l_-_n_a_m_e_s ssttaatteemmeenntt
-
- uussee--hhoosstt--ddeeccll--nnaammeess _f_l_a_g;;
-
- If the _u_s_e_-_h_o_s_t_-_d_e_c_l_-_n_a_m_e_s parameter is true in a given
- scope, then for every host declaration within that scope,
- the name provided for the host declaration will be sup-
- plied to the client as its hostname. So, for example,
-
- group {
- use-host-decl-names on;
-
-
-
-
- 10
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- host joe {
- hardware ethernet 08:00:2b:4c:29:32;
- fixed-address joe.fugue.com;
- }
- }
-
- is equivalent to
-
- host joe {
- hardware ethernet 08:00:2b:4c:29:32;
- fixed-address joe.fugue.com;
- option host-name "joe";
- }
-
- An _o_p_t_i_o_n _h_o_s_t_-_n_a_m_e statement within a host declaration
- will override the use of the name in the host declaration.
-
-RREEFFEERREENNCCEE:: OOPPTTIIOONN SSTTAATTEEMMEENNTTSS
- DHCP _o_p_t_i_o_n statements always start with the _o_p_t_i_o_n key-
- word, followed by an option name, followed by option data.
- The option names and data formats are described below.
- It is not necessary to exhaustively specify all DHCP
- options - only those options which are needed by clients
- must be specified.
-
- Option data comes in a variety of formats, as defined
- below:
-
- The iipp--aaddddrreessss data type can be entered either as an
- explicit IP address (e.g., 239.254.197.10) or as a domain
- name (e.g., haagen.isc.org). When entering a domain name,
- be sure that that domain name resolves to a single IP
- address.
-
- The iinntt3322 data type specifies a signed 32-bit integer.
- The uuiinntt3322 data type specifies an unsigned 32-bit integer.
- The iinntt1166 and uuiinntt1166 data types specify signed and
- unsigned 16-bit integers. The iinntt88 and uuiinntt88 data types
- specify signed and unsigned 8-bit integers. Unsigned
- 8-bit integers are also sometimes referred to as octets.
-
- The ssttrriinngg data type specifies an NVT ASCII string, which
- must be enclosed in double quotes - for example, to spec-
- ify a domain-name option, the syntax would be
-
- option domain-name "isc.org";
-
- The ffllaagg data type specifies a boolean value. Booleans
- can be either true or false (or on or off, if that makes
- more sense to you).
-
- The ddaattaa--ssttrriinngg data type specifies either an NVT ASCII
- string enclosed in double quotes, or a series of octets
- specified in hexadecimal, seperated by colons. For
-
-
-
- 11
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- example:
-
- option client-identifier "CLIENT-FOO";
- or
- option client-identifier 43:4c:49:45:54:2d:46:4f:4f;
-
- The documentation for the various options mentioned below
- is taken from the latest IETF draft document on DHCP
- options. Options which are not listed by name may be
- defined by the name option-_n_n_n, where _n_n_n _i_s _t_h_e _d_e_c_i_m_a_l
- _n_u_m_b_e_r _o_f _t_h_e _o_p_t_i_o_n _c_o_d_e_. _T_h_e_s_e _o_p_t_i_o_n_s _m_a_y _b_e _f_o_l_l_o_w_e_d
- _e_i_t_h_e_r _b_y _a _s_t_r_i_n_g_, _e_n_c_l_o_s_e_d _i_n _q_u_o_t_e_s_, _o_r _b_y _a _s_e_r_i_e_s _o_f
- _o_c_t_e_t_s_, _e_x_p_r_e_s_s_e_d _a_s _t_w_o_-_d_i_g_i_t _h_e_x_a_d_e_c_i_m_a_l _n_u_m_b_e_r_s _s_e_p_e_r_-
- _a_t_e_d _b_y _c_o_l_o_n_s_. _F_o_r _e_x_a_m_p_l_e_:
-
- option option-133 "my-option-133-text";
- option option-129 1:54:c9:2b:47;
-
- Because dhcpd does not know the format of these undefined
- option codes, no checking is done to ensure the correct-
- ness of the entered data.
-
- The standard options are:
-
- ooppttiioonn ssuubbnneett--mmaasskk _i_p_-_a_d_d_r_e_s_s;;
-
- The subnet mask option specifies the client's subnet mask
- as per RFC 950. If no subnet mask option is provided any-
- where in scope, as a last resort dhcpd will use the subnet
- mask from the subnet declaration for the network on which
- an address is being assigned. However, _a_n_y subnet-mask
- option declaration that is in scope for the address being
- assigned will override the subnet mask specified in the
- subnet declaration.
-
- ooppttiioonn ttiimmee--ooffffsseett _i_n_t_3_2;;
-
- The time-offset option specifies the offset of the
- client's subnet in seconds from Coordinated Universal Time
- (UTC).
-
- ooppttiioonn rroouutteerrss _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s ... ];;
-
- The routers option specifies a list of IP addresses for
- routers on the client's subnet. Routers should be listed
- in order of preference.
-
- ooppttiioonn ttiimmee--sseerrvveerrss _i_p_-_a_d_d_r_e_s_s _[_, _i_p_-_a_d_d_r_e_s_s ... ];;
-
- The time-server option specifies a list of RFC 868 time
- servers available to the client. Servers should be listed
- in order of preference.
-
- ooppttiioonn nnaammee--sseerrvveerrss _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s ... ];
-
-
-
- 12
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- The name-servers option specifies a list of IEN 116 name
- servers available to the client. Servers should be listed
- in order of preference.
-
- ooppttiioonn ddoommaaiinn--nnaammee--sseerrvveerrss _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s ...
- ];;
-
- The domain-name-servers option specifies a list of Domain
- Name System (STD 13, RFC 1035) name servers available to
- the client. Servers should be listed in order of prefer-
- ence.
-
- ooppttiioonn lloogg--sseerrvveerrss _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s ... ];;
-
- The log-server option specifies a list of MIT-LCS UDP log
- servers available to the client. Servers should be listed
- in order of preference.
-
- ooppttiioonn ccooookkiiee--sseerrvveerrss _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s ... ];;
-
- The cookie server option specifies a list of RFC 865
- cookie servers available to the client. Servers should be
- listed in order of preference.
-
- ooppttiioonn llpprr--sseerrvveerrss _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s ... ];;
-
- The LPR server option specifies a list of RFC 1179 line
- printer servers available to the client. Servers should
- be listed in order of preference.
-
- ooppttiioonn iimmpprreessss--sseerrvveerrss _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s ... ];;
-
- The impress-server option specifies a list of Imagen
- Impress servers available to the client. Servers should
- be listed in order of preference.
-
- ooppttiioonn rreessoouurrccee--llooccaattiioonn--sseerrvveerrss _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s
- ... ];;
-
- This option specifies a list of RFC 887 Resource Location
- servers available to the client. Servers should be listed
- in order of preference.
-
- ooppttiioonn hhoosstt--nnaammee _s_t_r_i_n_g;;
-
- This option specifies the name of the client. The name
- may or may not be qualified with the local domain name (it
- is preferable to use the domain-name option to specify the
- domain name). See RFC 1035 for character set restric-
- tions.
-
- ooppttiioonn bboooott--ssiizzee _u_i_n_t_1_6;;
-
- This option specifies the length in 512-octet blocks of
-
-
-
- 13
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- the default boot image for the client.
-
- ooppttiioonn mmeerriitt--dduummpp _s_t_r_i_n_g;;
-
- This option specifies the path-name of a file to which the
- client's core image should be dumped in the event the
- client crashes. The path is formatted as a character
- string consisting of characters from the NVT ASCII charac-
- ter set.
-
- ooppttiioonn ddoommaaiinn--nnaammee _s_t_r_i_n_g;;
-
- This option specifies the domain name that client should
- use when resolving hostnames via the Domain Name System.
-
- ooppttiioonn sswwaapp--sseerrvveerr _i_p_-_a_d_d_r_e_s_s;;
-
- This specifies the IP address of the client's swap server.
-
- ooppttiioonn rroooott--ppaatthh _s_t_r_i_n_g;;
-
- This option specifies the path-name that contains the
- client's root disk. The path is formatted as a character
- string consisting of characters from the NVT ASCII charac-
- ter set.
-
- ooppttiioonn iipp--ffoorrwwaarrddiinngg _f_l_a_g;;
-
- This option specifies whether the client should configure
- its IP layer for packet forwarding. A value of 0 means
- disable IP forwarding, and a value of 1 means enable IP
- forwarding.
-
- ooppttiioonn nnoonn--llooccaall--ssoouurrccee--rroouuttiinngg _f_l_a_g;;
-
- This option specifies whether the client should configure
- its IP layer to allow forwarding of datagrams with non-
- local source routes (see Section 3.3.5 of [4] for a dis-
- cussion of this topic). A value of 0 means disallow for-
- warding of such datagrams, and a value of 1 means allow
- forwarding.
-
- ooppttiioonn ppoolliiccyy--ffiilltteerr _i_p_-_a_d_d_r_e_s_s _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s
- _i_p_-_a_d_d_r_e_s_s ... ];;
-
- This option specifies policy filters for non-local source
- routing. The filters consist of a list of IP addresses
- and masks which specify destination/mask pairs with which
- to filter incoming source routes.
-
- Any source routed datagram whose next-hop address does not
- match one of the filters should be discarded by the
- client.
-
-
-
-
- 14
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- See STD 3 (RFC1122) for further information.
-
- ooppttiioonn mmaaxx--ddggrraamm--rreeaasssseemmbbllyy _u_i_n_t_1_6;;
-
- This option specifies the maximum size datagram that the
- client should be prepared to reassemble. The minimum
- value legal value is 576.
-
- ooppttiioonn ddeeffaauulltt--iipp--ttttll _u_i_n_t_8_;
-
- This option specifies the default time-to-live that the
- client should use on outgoing datagrams.
-
- ooppttiioonn ppaatthh--mmttuu--aaggiinngg--ttiimmeeoouutt _u_i_n_t_3_2;;
-
- This option specifies the timeout (in seconds) to use when
- aging Path MTU values discovered by the mechanism defined
- in RFC 1191.
-
- ooppttiioonn ppaatthh--mmttuu--ppllaatteeaauu--ttaabbllee _u_i_n_t_1_6 [,, _u_i_n_t_1_6 ... ];;
-
- This option specifies a table of MTU sizes to use when
- performing Path MTU Discovery as defined in RFC 1191. The
- table is formatted as a list of 16-bit unsigned integers,
- ordered from smallest to largest. The minimum MTU value
- cannot be smaller than 68.
-
- ooppttiioonn iinntteerrffaaccee--mmttuu _u_i_n_t_1_6;;
-
- This option specifies the MTU to use on this interface.
- The minimum legal value for the MTU is 68.
-
- ooppttiioonn aallll--ssuubbnneettss--llooccaall _f_l_a_g;;
-
- This option specifies whether or not the client may assume
- that all subnets of the IP network to which the client is
- connected use the same MTU as the subnet of that network
- to which the client is directly connected. A value of 1
- indicates that all subnets share the same MTU. A value of
- 0 means that the client should assume that some subnets of
- the directly connected network may have smaller MTUs.
-
- ooppttiioonn bbrrooaaddccaasstt--aaddddrreessss _i_p_-_a_d_d_r_e_s_s;;
-
- This option specifies the broadcast address in use on the
- client's subnet. Legal values for broadcast addresses are
- specified in section 3.2.1.3 of STD 3 (RFC1122).
-
- ooppttiioonn ppeerrffoorrmm--mmaasskk--ddiissccoovveerryy _f_l_a_g;;
-
- This option specifies whether or not the client should
- perform subnet mask discovery using ICMP. A value of 0
- indicates that the client should not perform mask discov-
- ery. A value of 1 means that the client should perform
-
-
-
- 15
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- mask discovery.
-
- ooppttiioonn mmaasskk--ssuupppplliieerr _f_l_a_g;;
-
- This option specifies whether or not the client should
- respond to subnet mask requests using ICMP. A value of 0
- indicates that the client should not respond. A value of
- 1 means that the client should respond.
-
- ooppttiioonn rroouutteerr--ddiissccoovveerryy _f_l_a_g;;
-
- This option specifies whether or not the client should
- solicit routers using the Router Discovery mechanism
- defined in RFC 1256. A value of 0 indicates that the
- client should not perform router discovery. A value of 1
- means that the client should perform router discovery.
-
- ooppttiioonn rroouutteerr--ssoolliicciittaattiioonn--aaddddrreessss _i_p_-_a_d_d_r_e_s_s;;
-
- This option specifies the address to which the client
- should transmit router solicitation requests.
-
- ooppttiioonn ssttaattiicc--rroouutteess _i_p_-_a_d_d_r_e_s_s _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s
- _i_p_-_a_d_d_r_e_s_s ... ];;
-
- This option specifies a list of static routes that the
- client should install in its routing cache. If multiple
- routes to the same destination are specified, they are
- listed in descending order of priority.
-
- The routes consist of a list of IP address pairs. The
- first address is the destination address, and the second
- address is the router for the destination.
-
- The default route (0.0.0.0) is an illegal destination for
- a static route. To specify the default route, use the
- rroouutteerrss option.
-
- ooppttiioonn ttrraaiilleerr--eennccaappssuullaattiioonn _f_l_a_g;;
-
- This option specifies whether or not the client should
- negotiate the use of trailers (RFC 893 [14]) when using
- the ARP protocol. A value of 0 indicates that the client
- should not attempt to use trailers. A value of 1 means
- that the client should attempt to use trailers.
-
- ooppttiioonn aarrpp--ccaacchhee--ttiimmeeoouutt _u_i_n_t_3_2;;
-
- This option specifies the timeout in seconds for ARP cache
- entries.
-
- ooppttiioonn iieeeeee880022--33--eennccaappssuullaattiioonn _f_l_a_g;;
-
- This option specifies whether or not the client should use
-
-
-
- 16
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- Ethernet Version 2 (RFC 894) or IEEE 802.3 (RFC 1042)
- encapsulation if the interface is an Ethernet. A value of
- 0 indicates that the client should use RFC 894 encapsula-
- tion. A value of 1 means that the client should use RFC
- 1042 encapsulation.
-
- ooppttiioonn ddeeffaauulltt--ttccpp--ttttll _u_i_n_t_8;;
-
- This option specifies the default TTL that the client
- should use when sending TCP segments. The minimum value
- is 1.
-
- ooppttiioonn ttccpp--kkeeeeppaalliivvee--iinntteerrvvaall _u_i_n_t_3_2;;
-
- This option specifies the interval (in seconds) that the
- client TCP should wait before sending a keepalive message
- on a TCP connection. The time is specified as a 32-bit
- unsigned integer. A value of zero indicates that the
- client should not generate keepalive messages on connec-
- tions unless specifically requested by an application.
-
- ooppttiioonn ttccpp--kkeeeeppaalliivvee--ggaarrbbaaggee _f_l_a_g;;
-
- This option specifies the whether or not the client should
- send TCP keepalive messages with a octet of garbage for
- compatibility with older implementations. A value of 0
- indicates that a garbage octet should not be sent. A value
- of 1 indicates that a garbage octet should be sent.
-
- ooppttiioonn nniiss--ddoommaaiinn _s_t_r_i_n_g;;
-
- This option specifies the name of the client's NIS (Sun
- Network Information Services) domain. The domain is for-
- matted as a character string consisting of characters from
- the NVT ASCII character set.
-
- ooppttiioonn nniiss--sseerrvveerrss _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s ... ];;
-
- This option specifies a list of IP addresses indicating
- NIS servers available to the client. Servers should be
- listed in order of preference.
-
- ooppttiioonn nnttpp--sseerrvveerrss _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s ... ];;
-
- This option specifies a list of IP addresses indicating
- NTP (RFC 1035) servers available to the client. Servers
- should be listed in order of preference.
-
- ooppttiioonn nneettbbiiooss--nnaammee--sseerrvveerrss _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s ...
- ];;
-
- The NetBIOS name server (NBNS) option specifies a list of
- RFC 1001/1002 NBNS name servers listed in order of prefer-
- ence.
-
-
-
- 17
-
-
-
-
-
-dhcpd.conf(5) dhcpd.conf(5)
-
-
- ooppttiioonn nneettbbiiooss--dddd--sseerrvveerr _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s ... ];;
-
- The NetBIOS datagram distribution server (NBDD) option
- specifies a list of RFC 1001/1002 NBDD servers listed in
- order of preference.
-
- ooppttiioonn nneettbbiiooss--nnooddee--ttyyppee _u_i_n_t_8;;
-
- The NetBIOS node type option allows NetBIOS over TCP/IP
- clients which are configurable to be configured as
- described in RFC 1001/1002. The value is specified as a
- single octet which identifies the client type. A value of
- 1 corresponds to a NetBIOS B-node; a value of 2 corre-
- sponds to a P-node; a value of 4 corresponds to an M-node;
- a value of 8 corresponds to an H-node.
-
- ooppttiioonn nneettbbiiooss--ssccooppee _s_t_r_i_n_g;;
-
- The NetBIOS scope option specifies the NetBIOS over TCP/IP
- scope parameter for the client as specified in RFC
- 1001/1002. See RFC1001, RFC1002, and RFC1035 for charac-
- ter-set restrictions.
-
- ooppttiioonn ffoonntt--sseerrvveerrss _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s ... ];;
-
- This option specifies a list of X Window System Font
- servers available to the client. Servers should be listed
- in order of preference.
-
- ooppttiioonn xx--ddiissppllaayy--mmaannaaggeerr _i_p_-_a_d_d_r_e_s_s [,, _i_p_-_a_d_d_r_e_s_s ... ];;
-
- This option specifies a list of systems that are running
- the X Window System Display Manager and are available to
- the client. Addresses should be listed in order of pref-
- erence.
-
- ooppttiioonn ddhhccpp--cclliieenntt--iiddeennttiiffiieerr _d_a_t_a_-_s_t_r_i_n_g;;
-
- This option can be used to specify the a DHCP client iden-
- tifier in a host declaration, so that dhcpd can find the
- host record by matching against the client identifier.
-
-SSEEEE AALLSSOO
- dhcpd.conf(5), dhcpd.leases(5), draft-ietf-dhc-
- options-1533update-04.txt, draft-ietf-dhc-dhcp-07.txt.
-
-AAUUTTHHOORR
- ddhhccppdd((88)) was written by Ted Lemon <mellon@vix.com> under a
- contract with Vixie Labs. Funding for this project was
- provided by the Internet Software Corporation. Informa-
- tion about the Internet Software Consortium can be found
- at hhttttpp::////wwwwww..iisscc..oorrgg//iisscc..
-
-
-
-
-
- 18
-
-